Novel Torque Control Technique for High Efficiency/High Power Interior Permanent Magnet Synchronous Motors

HV The motors of hybrid electric vehicles must be able to offer high efficiency, a high power/weight ratio, and excellent reliability across the entire rotor speed range. Interior permanent magnet synchronous (IPM) motors are used to satisfy these requirements. The goal of this study was to develop an IPM motor control method that would increase the torque and the efficiency at high and medium rotor speeds. A method for increasing the torque and efficiency at high speeds was described in a previous paper, and is known as voltage phase compensation (VPC). The method described in the previous paper involved combining VPC with normal current compensation to control the torque across the entire range of speeds, and to increase the torque at high speeds. This method failed, however, to achieve sufficient torque at mid-range speeds. This paper introduces a new type of compensation (Overmodulation Current Compensation: OCC) that increases the torque at midrange speeds while achieving current control in the overmodulation range of the inverter. Combining the conventional current compensation, VPC, with OCC achieves an increase in the torque and the efficiency at both highand mid-range rotor speeds. The type of compensation applied is switched automatically by using the proposed transitional algorithm. This paper shows the validity of the proposed method by using the experimental evaluations.